Background: Symptomatic intracranial atherosclerotic disease (ICAD) is associated with high risk for recurrent stroke. Identification of patients remains a challenge using clinical and radiographic markers. Recent research has identified signal intensity ratio (SIR) across stenotic lesions on time-of-flight magnetic resonance angiography (TOF-MRA) as a novel noninvasive marker of recurrent stroke risk. We sought to externally validate this approach in a single center analysis.
Methods: From a prospective observational stroke registry since August 2012, we identified patients with ischemic stroke due to ICAD causing moderate-severe stenosis of the basilar, intracranial vertebral, intracranial internal carotid, or middle cerebral arteries. Using the method described previously, we calculated SIR values across the stenotic lesions corrected for background signal intensity from TOF-MRA performed within 7 days of index stroke admission. Outcomes were prospectively captured by phone interview at 1 and 3 months after stroke. Recurrent stroke was defined by new infarct in the territory of the stenotic artery or absent imaging confirmation, territory-specific clinical symptoms lasting > 24 hours. We evaluated whether baseline SIR values were different between patients with and without recurrent stroke overall and in subgroups by ICAD location. P-value < 0.05 was considered significant.
Results: Among 99 consecutive patients with ICAD, 79 (80%) had interpretable MRAs at baseline (mean age 68.4 +11.2 years, 53.2% male, 53.2% black, median NIHSS score 3; 27.7% posterior circulation stenosis). Recurrent stroke occurred in 21.5% and 25.3% of patients at 1 and 3 months, respectively. Median SIR at baseline was 0.86 (interquartile range 0.56-1.04) and was not different those with vs. without recurrent stroke (1-month: 0.79 vs. 0.86, p=0.93; 3-month: 0.79 vs. 0.86, p=0.68). Results were not different by ICAD location.
Discussion: In this single center prospective registry, we were unable to validate SIR on time-of-flight MRA as a marker of early recurrent stroke risk in patients with symptomatic ICAD. Further research is needed to identify novel predictors of recurrence in this high-risk cohort.